Flash layer overcoat for magnetically-induced super resolution magneto-optical media

ABSTRACT

Magnetically-induced, super-resolution (MSR), magneto-optical (MO) information storage media having improved tribological properties when used in high-density storage devices employing very small head flying heights are formed by providing a protective flash layer overcoat (FLO)/lubricant topcoat layer system on the media surface. Embodiments of the present invention include forming the FLO layer of an amorphous, abrasion-resistant, carbon-based, diamond-like material not greater than about 10 Å thick and selected from CN x , CH x , and CN x H y , and providing the lubricant topcoat as an about 15-25 Å thick layer of a fluoropolyether or perfluoropolyether compound, e.g., perfluoropolyethylene (PFPE).

CROSS-REFERENCE TO PROVISIONAL APPLICATION

This application claims priority from provisional patent applicationSer. No. 60/107,698 filed Nov. 9, 1998, the entire disclosure of whichis incorporated herein by reference.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application contains subject matter similar to subject matterdisclosed in co-pending U.S. patent applications Ser. No. 09/433,375,filed on Nov. 3, 1999; Ser. No. 09/433,376, filed on Nov. 3, 1999; andSer. No. 09/433,378, filed on Nov. 3, 1999.

FIELD OF THE INVENTION

The present invention relates to the recording, storage, and reading ofinformation utilizing magneto-optical (MO) media, particularly rotatableMO storage media, such as in the form of thin film disks, and aprotective overcoat/lubricant topcoat layer system for contact withcooperating transducer and/or sensor heads or devices.

BACKGROUND OF THE INVENTION

In recent years, much research and development of MO recording media foruse as high density/high capacity memory devices has been carried out.Such media typically comprise a suitable substrate, e.g., of glass,polymer, metal, or ceramic material, coated with a perpendicularlymagnetizable film used as a recording medium. Information is recordedwithin the medium by switching the direction of magnetization of desiredportions (i.e., domains) of the perpendicularly magnetizable film. Morespecifically, for recording information, the recording medium is firstinitialized by applying to the medium a magnetic field from anexternally positioned magnetic field generation device (i.e., externalmagnetic bias), thereby making the direction of the perpendicularmagnetization uniformly upwardly or downwardly facing. A first laserbeam of sufficiently high power or intensity from a suitable source,e.g., a laser diode, is then irradiated on desired recording portions ofthe recording medium in the presence of an externally applied magneticbias field. As a consequence of the laser beam irradiation, thetemperature of the irradiated portions (domains) of the recording mediumrises, and when the temperature reaches or exceeds the Curie point ofthe vertically magnetizable film or its magnetic compensation point, thecoercive force on the recording portion becomes zero or substantiallyzero. When this state is achieved at the desired recording portions ofthe medium, and in the presence of the externally biased magnetic field,the direction of the perpendicular magnetization is switched, e.g., fromupwardly facing (=digital logic 1 or 0) to downwardly facing (=digitallogic 0 or 1, respectively) or vice versa, so as to be aligned with thatof the external magnetic field. At the end of a write pulse (i.e., laserpulse), the temperature of the heated recording domain then decreasesand eventually returns to room temperature by cessation of the laserbeam irradiation thereof. Since the alignment direction of magnetizationof the recording media effected by the laser pulse heating to above theCurie temperature is maintained at the lowered temperature, desiredinformation can thus be recorded in the magneto-optical media.

For reading the information stored in the MO media according to theabove-described method, the recorded portions of the media areirradiated with a second, linearly polarized laser beam of lower poweror intensity than the one used for recording, and light reflected ortransmitted from the recorded portions is detected, as by a suitabledetector/sensor means. The recorded information is read out by detectingthe Kerr rotation angle of the polarization plane of light reflectedfrom the recording layer or the Faraday rotation angle of thepolarization plane of light transmitted through the recording layer.More particularly, since the rotation angle of the polarization planevaries depending upon the direction of magnetization of the recordedportions of the media according to the Kerr or Faraday effect,information stored within the media can be read out optically by adifferential detector which decodes the polarization-modulated lightbeam into bits of information.

Such MO recording media, when fabricated in disk form for rotation abouta central axis, can be adapted for use in conventional Winchester, orhard drive, devices as are employed with conventional magnetic recordingmedia. Hard drives typically employed for such disk-shaped media utilizeflying heads for mounting transducer/sensor devices, etc., thereon, forclose positioning thereof adjacent the surface of the recording media.In operation, a typical contact start/stop (CSS) method commences when adata transducing head begins to slide against the surface of the disk asthe disk begins to rotate. Upon reaching a predetermined high rotationalspeed, the head floats in air at a predetermined small distance from thesurface of the disk, where it is maintained during reading and recordingoperations. Upon terminating operation of the disk drive, the head againbegins to slide against the surface of the disk and eventually stops incontact with and pressing against the disk. Therefore, as in the case ofmagnetic disks, a lubricant (optionally with an underlying protectivelayer) is typically applied to the disk surface for minimizingscratching and abrasion of the sensor/transducer head and the recordingmedia surface, which can result in an undesirably high wear rate of thehead and recording media surface.

However, in the case of portable MO recording devices, the use of alubricating oil, e.g., a fluorocarbon-based oil, is problematic in thatit is difficult to maintain the lubricating oil on the surface of the MOmedia, thereby increasing surface scratching and wear. In addition, MOdisks produced without lubricating oil on their surface by somemanufacturers are not necessarily compatible with similar media producedwith lubricating oil by other manufacturers.

In another approach for minimizing abrasion, scratching, and wear oftransducer heads, a solid lubricant is applied to the bottom surface ofthe flying head which comes into contact with the surface of the MOrecording medium. However, such solid lubricant applied to the bottomsurface of the flying head must have a durability many times greaterthan lubricant applied to the MO recording medium. As a consequence,application of solid lubricant only to the flying head is not sufficientfor adequately reducing abrasion, scratching, and wear.

An additional difficulty encountered in the development ofwear-resistant, lubricated MO recording media and Winchester-type drivestherefor, is the requirement imposed by the impetus for achievingever-higher density recording, which necessitates further reduction inthe disk-transducer/sensor spacing. The head-to-disk interface (HDI)becomes very critical as head-disk spacing is reduced and head flyheight decreases. Conventional MO media without a protective overcoatand lubricant layer have extremely poor tribological performance,resulting in lack of reliability of MO-based disk drives.

The above-described problems, including disk crashing during headloading, associated with the requirement for reduced head-disk spacingand fly height, are further exacerbated in the case ofmagnetically-induced super resolution (“MSR”) MO media wherein enhancedrecording density is provided by interposing an exchange coupling forcelayer or a static coupling layer between the MO writing and read-outlayers, as will be further described in more detail below.

Thus, there exists a need for a protective overcoat or protectiveovercoat/lubricant topcoat layer system which enables the manufacture ofreliable, very high density recording magnetically-induced,super-resolution, MO-based disk drives, which layer system effectivelyeliminates the problems and drawbacks associated with the conventionaltechnology, i.e., scratching, abrasion, brittleness, increased wear oftransducer/sensor head and recording media surfaces, and tendency forcrashing during head loading.

The present invention addresses and solves the problems attendant uponthe use of magnetically induced, super-resolution, MO-based disk-shapedrecording media and hard drives, while maintaining full compatibilitywith all mechanical aspects of conventional disk drive technology.

DISCLOSURE OF THE INVENTION

An advantage of the present invention is a high density,magnetically-induced, super-resolution, MO-based recording medium havingimproved tribological performance and long-term durability.

Another advantage of the present invention is a magnetically-induced,super-resolution, MO-based recording medium having an improvedprotective overcoat layer.

A further advantage of the present invention is a magnetically-induced,super-resolution, MO-based recording medium having an improvedprotective overcoat/lubricant topcoat layer system.

Yet another advantage of the present invention is amagnetically-induced, super-resolution, MO-based, disk-shaped recordingmedium providing improved performance at decreased head-to-diskspacings.

Still another advantage of the present invention is single- anddual-sided magnetically-induced, super-resolution, MO-based media havingprotective overcoat layer/lubricant topcoat layer systems thereonproviding improved ribological performance.

Additional advantages and other features of the present invention willbe set forth in the description which follows and in part will becomeapparent to those having ordinary skill in the art upon examination ofthe following or may be learned from practice of the present invention.The advantages of the present invention may be realized and obtained asparticularly pointed out in the appended claims.

According to one aspect of the present invention, the foregoing andother advantages are obtained in part by a magnetically-induced,super-resolution, MO storage medium including at least one laminate oflayers comprising, in sequence from a substrate surface: an MO writinglayer; an MO exchange coupling layer or a dielectric layer formagneto-static coupling between the MO writing layer and a MO read-outlayer for increasing the recording density; an MO read-out layer; adielectric layer which is transparent to the wavelength(s) of at leastone laser beam used for writing and reading out information stored inthe medium; and an amorphous, abrasion resistant, carbon-basedprotective overcoat layer over the transparent dielectric layer.

According to embodiments of the present invention, the amorphous,abrasion resistant protective overcoat layer has a thickness not greaterthan about 10 Å thick, e.g., from about 5 to about 10 Å and comprises adiamond-like material selected from a-CN_(x), a-CH_(x), anda-CN_(x)H_(y); and the laminate further comprises a lubricant topcoatlayer on the protective overcoat layer, the lubricant topcoat layercomprising a fluoropolyether or a perfluoropolyether compound and havinga thickness of from about 15 to about 25 Å.

According to further embodiments of the present invention, the substrateincludes a pair of opposed major surfaces and comprises a materialselected from the group consisting of polymers, metals, glass, andceramics; the laminate of layers comprises a set of layers formed on oneof the pair of opposed major surfaces, the layer set comprising, inoverlying sequence from the substrate:

(a) a reflective, heat sinking layer formed on one of the pair ofopposed major surfaces of the substrate;

(b) a first dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength;

(c) an MO auxiliary, writing assist layer comprising a rareearth/transition metal (RE/TM) material;

(d) an MO writing layer comprising an RE/TM thermo-magnetic materialhaving perpendicular anisotropy, large perpendicular coercivity, andhigh Curie temperature;

(e) an MO exchange coupling layer comprising an RE-TM material, forreplicating the magnetic orientation of the MO writing layer and therebyincreasing the coupling force between the MO writing layer and the MOread-out layer; or

(f) a second dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength andperforms magneto-static coupling between MO writing and read-out layers;

(g) an MO read-out layer comprising an RE-TM material having a smallcoercivity; and

(h) a third dielectric layer comprising a material which issubstantially transparent to the at least one laser beam wavelength;

wherein the protective overcoat layer is formed on the third dielectriclayer and the lubricant topcoat layer is formed over the protectiveovercoat layer.

According to embodiments of the present invention:

the reflective, heat sinking layer (a) comprises aluminum (Al) or analloy thereof;

each of the first, second, and third substantially transparentdielectric layers (b), (f), and (h) comprises a material selected fromthe group consisting of: SiN_(x), AlN_(x), SiO_(x), and AlO_(x);

the MO auxiliary, writing assist layer (c) comprises an RE-TM materialselected from the group consisting of TbFe, TbFeCo, and FeCoX, where Xis Dy, Gd, or Sm;

the MO writing layer (d) comprises an RE-TM material selected from thegroup consisting of: TbFe, TbFeCo, TbFeCoX, TbDyFeCo, and TbDyFeCoX,where X is Al, Y, or Nd, and DyFeCoX, where X is Y, Nd, or Al;

the MO exchange coupling layer (e) comprises an RE-TM material selectedfrom the group consisting of: Gd, GdFe, GdFeSi, and GdFeAl; and

the MO read-out layer (g) comprises an RE-TM material having in-planemagnetization at room temperature, selected from the group consistingof: GdFeCo and GdFeCoX, where X is Al, Nd, or Y, and GdFeCoXX′, where Xis Al, Nd, or Y and X′ is Cr, Ta, or Nb.

In a further embodiment according to the present invention, the mediumcomprises another layer stack, identical to the above-described layerstack, formed on the other one of the pair of opposed major surfaces ofthe substrate.

According to another aspect of the present invention, amagnetically-induced, super-resolution magneto-optical (MO) storagemedium includes at least one laminate of layers comprising, in sequencefrom a substrate surface, an MO writing assist layer, an MO writinglayer, an MO exchange coupling layer or a magneto-static coupling layerfor increasing the writing density, an MO read-out layer, and adielectric layer which is substantially transparent to the wavelength(s)of at least one laser beam used for writing and reading-out informationstored in the medium, the medium further comprising:

an amorphous, abrasion-resistant, carbon-based, protective overcoat overthe transparent dielectric layer, the protective overcoat layer having athickness not greater than about 10 Å and comprising a diamond-likematerial selected from the group consisting of: a-CN, a-CH_(x), anda-CN_(x)H_(y); and

a lubricant topcoat layer having a thickness of from about 15 to about25 Å on the protective overcoat layer, the lubricant topcoat layercomprising a fluoropolyether polymer or a perfluoropolyether polymer.

According to yet another aspect of the present invention, amagnetically-induced, super-resolution (MSR), magneto-optical (MO)storage medium includes:

a substrate; and

means for protecting the exterior surface of the medium.

Additional advantages of the present invention will become readilyapparent to those skilled in the art from the following detaileddescription, wherein only preferred embodiments of the invention areshown and described, simply by way of illustration of the best modecontemplated for practicing the present invention. As will be described,the present invention is capable of other and different embodiments, andits several details are susceptible of modification in various obviousrespects, all without departing from the spirit of the presentinvention. Accordingly, the drawing and description are to be regardedas illustrative in nature, and not as limitative.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of the embodiments of the presentinvention can best be understood when read in conjunction with thefollowing drawings, in which like reference numerals are employedthroughout to designate similar features, wherein:

FIG. 1 illustrates, in simplified, cross-sectional schematic form, a MOmedium according to a single-sided embodiment according to the presentinvention;

FIG. 2 illustrates, in simplified, cross-sectional schematic form, a MOmedium according to a dual-sided embodiment according to the presentinvention.

It should be recognized that the various layers forming the layer stacksor laminates in the appended figures representing cross-sections ofportions of MO media fabricated according to the inventive methodologyare not drawn to scale, but instead are drawn as to best illustrate thefeatures of the present invention.

BACKGROUND OF THE INVENTION

The present invention is based on the discovery that an ultra-thin,“flash-layer” protective overcoat (“FLO”) and FLO protectiveovercoat/lubricant topcoat layer system comprised of specific materialscan provide optimal tribological performance of magnetically-induced,super-resolution (“MSR”) MO-based media, such as disks, with minimallubricant topcoat layer thicknesses and head-to-disk spacings (i.e.,flying heights) less than about 2 microinches (μ inch) for media withpolymeric substrates; less than about 1μ inch for media with metal,glass, or ceramic substrates with Ra of from about 3 to about 5Angstroms; and less than about 0.5μ inch for media with glass,glass-ceramic, or ceramic substrates with Ra of from about 2 to about 3Å More specifically, according to the present invention, an ultra-thinFLO layer comprising an amorphous, hard, carbon-based,abrasion-resistant protective material, e.g., a carbon-baseddiamond-like material such as a-CN_(x) (where x=0.05-0.30), a-CH_(x)(where x=0.20-0.30), and a-CN_(x)H_(y) (where x=0.03-0.10 andy=0.15-0.30), is formed to cover the uppermost transparent dielectriclayer, typically a SiN_(x) material, formed over the MO read-out layerof such type MO media. The amorphous, diamond-like protective overcoatlayer has a thickness not greater than about 10 Å, e.g., about 5 toabout 10 Å, and can be formed by any of the physical vapor deposition(PVD) or chemical vapor deposition (CVD) methods conventionally employedfor depositing such type layers. By way of illustration, but notlimitation, a-CH_(x) layers may be deposited on suitable dielectricallycoated MO media substrates by AC sputtering of a 3 inch by 15 inchgraphite target at frequencies in the range of 40-400 KHz at a power inthe range of 0.5-2 KW in an atmosphere of 15% H₂/85% Ar. Similarconditions may be employed for forming a-CN_(x) and a-CN_(x)H_(y)coatings by use of N₂ and H₂—N₂ mixtures, respectively. Given thepresent disclosure and the objectives of the invention, determinationand selection of the parameters necessary for obtaining equivalentlyperforming diamond-like amorphous carbon-containing coatings by otherconventional film-forming techniques is considered within the ambit ofthe artisan for use in a particular situation.

The lubricant topcoat layer formed over the protective overcoat layer,in embodiments according to the present invention, comprisesfluoropolyether or perfluoropolyether polymers such as, for example,perfluoropolyethylene (PFPE), and like materials available under thetradenames Fomblin ZDol, Fomblin AM2001, and Fomblin Z-Dol TX fromAusimont, Thorofare, N.J., and has a thickness not greater than about 25Å, e.g., from about 10 to about 25 Å.

The lubricant topcoat layer can be applied in any conventional manner,as by dipping in a dilute solution of the lubricant in a suitablesolvent, e.g., a hydrofluorocarbon, or by spraying, etc. Desirably, thesurface of the disk is preliminarily treated to be free of impurities sothat good bonding can occur between the functional end groups of thelubricant polymer molecules and the substrate surface (i.e., theprotective overcoat layer). The bonding of the lubricant to the surfaceof the disk can be enhanced by cleaning the surface of the protectiveovercoat layer with a mild plasma or a solvent rinse prior to applyingthe lubricant.

By way of illustration, but not limitation, magnetically-induced,super-resolution (MSR) MO media provided with a 5-10 Å thick amorphous,carbon-based, diamond-like protective overcoat layer selected froma-CH_(x), a-CN_(x), and a-CN_(x)H_(y) and coated with 15-25 Å thicklubricant topcoat layers of Fomblin Zdol and Fomblin AM2001, providedexcellent tribological and stiction properties at reduced fly heights offrom about 2 to about 5μ inches for media with polymeric substrates andfrom about 0.5 to about 2μ inches for media with metal, glass, orceramic substrates.

An embodiment of the present invention comprises a single-sided,magnetically-induced, super-resolution (MSR) MO medium 10 employing theinventive flash layer protective overcoat (FLO) and FLO/lubricanttopcoat layer system and is illustrated in FIG. 1, wherein referencenumeral 1 denotes a substrate comprising a pair of major opposedsurfaces 1A and 1B. The material of the substrate is not critical forthe practice of the invention, and may be selected from polymers,metals, glass, and ceramics. The thickness of substrate 1 is also notcritical, but must provide adequate rigidity during rotation and staticperiods.

Formed on a first one (1A) of the opposing major surfaces of substrate 1is a layer stack, comprising, in overlying sequence from substratesurface 1A: (a) a reflective, heat-sinking layer 2 about 300-700 Åthick, preferably about 500 Å thick, typically comprising Al or an alloythereof, e.g., AlCr, AlTi, etc.; (b) a first dielectric material layer 3about 100-400 Å thick, preferably about 100-200 Å thick, andsubstantially transparent to the wavelength(s) of the at least one laserbeam employed for writing and reading out information, typicallyselected from SiN_(x) (where x=ca. 0.8-1.33), AlN_(x) (where x=ca.1-1.5), SiO_(x) (where x=ca. 1-2.0), and AlO_(x) (where x=ca. 1-1.5);(c) a MO auxiliary, writing assist layer 4 comprising a RE-TM materialabout 50-100 Å thick, typically selected from TbFe, TbFeCo, and FeCoX,where X is Dy, Gd, or Sm; (d) a MO writing layer 5 comprising a RE-TMmaterial about 200-300 Å thick and having perpendicular anisotropy,large perpendicular coercivity, and high Curie temperature, typicallyselected from TbFe, TbFeCo, TbDyFeCo, TbFeCoX, and TbDyFeCoX, where X isAl, Y, or Nd, and DyFeCoX, where X is Y, Nd, or Al; (e) an MO exchangecoupling layer 6 comprising a RE-TM material about 10-50 Å thick, forreplicating the magnetic orientation of the MO writing layer 5 andthereby increasing the coupling force between the MO writing layer 5 andthe MO read-out layer 8, typically selected from Gd, GdFe, GdFeSi andGdFeAl; or (f) a second dielectric material layer 7, for performingmagneto-static coupling between MO writing layer 5 and MO read-out layer8, the second dielectric layer 7 being about 5-50 Å thick andsubstantially transparent to the wavelength(s) of the at least one laserbeam employed for writing and reading out information, typicallyselected from SiN_(x), AlN_(x), SiO_(x), and AlO_(x), where x in eachinstance is as given above for layer 3; (g) a MO readout layer 8comprising a RE-TM material about 200-400 Å thick, typically selectedfrom GdFeCo and GdFeCoX, where X is Al, Nd, or Y, and GdFeCoXX′, where Xis Al, Nd, or Y, and X′ is Cr, Ta, or Nb; (h) a third dielectricmaterial layer 9, substantially transparent to the wavelength(s) of theat least one laser beam employed for writing and reading outinformation, i.e., about 400-500 Å for blue lasers and about 800-1200 Åfor red lasers, typically selected from SiN_(x), AlN_(x), SiO_(x), andAlO_(x), where x in each instance is as given above for layer 3; (i) anamorphous, diamond-like protective overcoat layer 11 not greater thanabout 10 Å Å thick, typically about 5 to about 10 Å thick and comprisinga material as described supra, i.e., a-CN_(x) (where x=0.05-0.30),a-CH_(x) (where x=0.20-0.30), or a-CN_(x)H_(y) (where x=0.03-0.10 andy=0.15-0.30); and (j) a lubricant topcoat layer 12 having a thickness ofabout 15-25 Å and comprised of a fluoropolyether or perfluoropolyetherpolymer compound, e.g., perfluoropolyethylene (PFPE).

It should be noted that MSR-MO media, such as described above, can havetwo alternate layer configurations, i.e., a magnetic exchange couplingconfiguration utilizing MO exchange coupling layer 6 and not requiringsecond dielectric layer 7, and a magneto-static coupling configurationutilizing second dielectric layer 7 and not requiring MO exchangecoupling layer 6.

FIG. 2 illustrates another, dual-sided embodiment corresponding to thesingle-sided, first embodiment shown in FIG. 1 and described above. Suchdual-sided media advantageously may be operated to record and read outinformation from both sides of a common substrate, and thus are usefulfor increasing storage density. As for the dual-sided embodiment of FIG.2, medium 20 comprises a second layer stack formed on the second majorsurface 1B of substrate 1, in opposing relation to the first layer stackformed on the first major surface 1A, with both layer stacks beingidentically constituted as shown in FIG. 1.

Conventional techniques, such as PVD and/or CVD may be employed fordepositing each of the reflective, dielectric, auxiliary, writing,exchange coupling, and read-out MO RE-TM layers, as well as theprotective overcoat layers of the layer stacks of the above-describedembodiments, with sputtering generally being preferred. The lubricanttopcoat layer is readily deposited by conventional dipping techniques,as indicated above. Therefore, details of the deposition techniquesutilized for forming each of the layers of the layer stack are generallyomitted from the present disclosure for brevity and in order not tounnecessarily obscure the present invention.

Thus, the present invention advantageously provides, as by the use ofconventional processing techniques, high quality, magnetically-induced,super-resolution, MO information storage media having novel, ultra-thin,abrasion-resistant, carbon-based, flash layer overcoats (FLO) impartingimproved tribological properties thereto and therefore suitable for usein high density storage devices requiring minimal head fly height.

In the previous description, numerous specific details are set forth,such as specific materials, structures, reactants, processes, etc., inorder to provide a better understanding of the present invention.However, the present invention can be practiced without resorting to thedetails specifically set forth. In other instances, well-knownprocessing materials and techniques have not been described in detail inorder not to unnecessarily obscure the present invention.

Only the preferred embodiments of the present invention and but a fewexamples of its versatility are shown and described in the presentdisclosure. It is to be understood that the present invention is capableof use in various other combinations and environments and is susceptibleof changes and/or modifications within the scope of the inventiveconcept as expressed herein.

What is claimed is:
 1. A magnetically-induced, super-resolution (MSR),magneto-optical (MO) storage medium including at least one laminate oflayers comprising, in sequence from a substrate surface: an MO writinglayer; an MO exchange coupling layer or a magneto-static coupling layerfor increasing the recording density; an MO read-out layer; a dielectriclayer which is substantially transparent to the wavelength(s) of atleast one laser beam used for writing and reading out information storedin said medium; and an amorphous, abrasion resistant, carbon-basedprotective overcoat layer over said transparent dielectric layer.
 2. Themedium according to claim 1, wherein: said abrasion resistant protectiveovercoat layer comprises a material selected from the group consistingof: a-CN_(x), where x=0.05-0.30; a-CH_(x), where x=0.20-0.30; anda-CN_(x)H_(y), where x=0.03-0.10 and y=0.15-0.30.
 3. The mediumaccording to claim 2, wherein said protective overcoat layer has athickness not greater than about 10 Å.
 4. The medium according to claim2, wherein said protective overcoat layer has a thickness of from about5 to about 10 Å.
 5. The medium according to claim 1, wherein saidlaminate further comprises a lubricant topcoat layer on said protectiveovercoat layer.
 6. The medium according to claim 5, wherein saidlubricant topcoat layer comprises a fluoro polyether or perfluoropolyether lubricant.
 7. The medium according to claim 6, wherein saidlubricant topcoat layer has a thickness of from about 15 to about 25 Å.8. The medium according to claim 1, wherein said substrate includes apair of opposed major surfaces and comprises a material selected fromthe group consisting of: polymers, metals, glass, and ceramics.
 9. Themedium according to claim 8, wherein said laminate of layers comprises astack of layers formed on one of said pair of opposed major surfaces,said layer stack comprising, in overlying sequence from said substrate:(a) a reflective, heat sinking layer formed on one of said pair ofopposed major surfaces of said substrate; (b) a first dielectric layercomprising a material which is substantially transparent to said atleast one laser beam wavelength; (c) an MO auxiliary, writing assistlayer comprising a rare earth/transition metal (RE-TM) material; (d) anMO writing layer comprising an RE-TM thermo-magnetic material havingperpendicular anisotropy, large perpendicular coercivity, and high Curietemperature; (e) an MO exchange coupling layer comprising an RE-TMmaterial, for replicating the magnetic orientation of the MO writinglayer and thereby increasing the coupling force between the MO writinglayer and the MO read-out layer; or (f) a magneto-static coupling layercomprising a second dielectric layer comprising a material which issubstantially transparent to said at least one laser beam wavelength andperforms exchange decoupling; (g) an MO read-out layer comprising anRE-TM material having a small coercivity; and (h) a third dielectriclayer comprising a material which is substantially transparent to saidat least one laser beam wavelength; wherein said protective overcoatlayer is formed on said third dielectric layer.
 10. The medium accordingto claim 9, further comprising a lubricant topcoat layer over saidprotective overcoat layer.
 11. The medium according to claim 9, wherein:said reflective, heat sinking layer (a) comprises aluminum or an alloythereof; each of said first, second, and third substantially transparentdielectric layers (b), (f), and (h) comprises a material selected fromthe group consisting of: SiN_(x), where x=0.8-1.33; AlN_(x), where x=ca.1-1.5; SiO_(x), where x=ca. 1-2.0; and AlO_(x), where x=ca. 1-1.5; saidMO auxiliary, writing assist layer (c) comprises an RE-TM materialselected from the group consisting of: TbFe, TbFeCo, and FeCoX, where Xis Dy, Gd, or Sm; said MO writing layer (d) comprises an RE-TM materialselected from the group consisting of: TbFe, TbFeCo, TbDyFeCo, TbFeCoX,and TbDyFeCoX, where X is Al, Y, or Nd, and DyFeCoX, where X is Y, Nd,or Al; said MO exchange coupling layer (e) comprises an RE-TM materialselected from the group consisting of Gd, GdFe, GdFeSi, and GdFeAl; andsaid MO read-out layer (g) comprises an RE-TM material selected from thegroup consisting of: GdFeCo and GdFeCoX, where X is Al, Nd, or Y, andGdFeCoXX′, where X is Al, Nd, or Y and X′ is Cr, Ta, or Nb.
 12. Themedium according to claim 11, comprising another layer stack, identicalto the abovesaid layer stack, formed on the other one of said pair ofopposed major surfaces of said substrate.
 13. A magnetically-induced,super-resolution, magneto-optical (MO) storage medium including at leastone laminate of layers comprising, in sequence from a substrate surface:an MO writing assist layer; an MO writing layer; an MO exchange couplinglayer or a magneto-static coupling layer in contact with the MO writinglayer for increasing the recording density thereof; an MO read-outlayer; a dielectric layer which is substantially transparent to thewavelength(s) of at least one laser beam used for writing andreading-out information stored in said medium; an amorphous, abrasionresistant, carbon-based, protective overcoat layer over said transparentdielectric layer, said protective overcoat layer having a thickness notgreater than about 10 Å and comprising a diamond-like material selectedfrom the group consisting of: a-CN_(x), where x=0.05-0.30; a-CH_(x),where x=0.20-0.30; and a-CN_(x)H_(y), where x=0.03-0.10 and y=0.15-0.30;and a lubricant topcoat layer having a thickness of from about 15 Å toabout 25 Å on said protective overcoat layer, said lubricant topcoatlayer comprising a fluoro polyether polymer or a perfluoro polyetherpolymer.
 14. The medium according to claim 13, wherein said substrateincludes a pair of opposed major surfaces and comprises a materialselected from the group consisting of: polymers, metals, glass, andceramics.
 15. The medium according to claim 14, wherein said laminate oflayers comprises a stack of layers formed on one of said pair of opposedmajor surfaces, said layer stack comprising, in overlying sequence fromsaid substrate: (a) a reflective, heat sinking layer formed on said oneof said pair of opposed major surfaces of said substrate and comprisingaluminum or an alloy thereof; (b) a first dielectric layer comprising amaterial which is substantially transparent to said at least at leastone laser beam wavelength and selected from the group consisting of:SiN_(x), where x=ca. 0.8-1.33; AlN_(x), where x=ca. 1-1.5; SiO_(x),where x=ca. 1-2.0; and AlO_(x), where x=ca. 1-1.5; (c) an MO auxiliary,writing assist layer comprising an RE-TM material selected from thegroup consisting of: TbFe, TbFeCo, and FeCoX, where X is Dy, Gd, or Sm;(d) an MO writing layer comprising an RE-TM themo-magnetic materialhaving perpendicular anisotropy, large perpendicular coercivity, highCurie temperature, and selected from the group consisting of: TbFe,TbFeCo, TbFeCoX, TbDyFeCo, and TbDyFeCoX, where X is Al, Nd, or Y, andDyFeCoX, where X is Al, Nd, or Y; (e) an MO exchange coupling layercomprising an RE-TM material comprising Gd, GdFe, GdFeSi, or GdFeAl, forreplicating the magnetic orientation of the MO writing layer and therebyincreasing the coupling force between the MO writing layer and the MOread-out layer; or (f) a magneto-static coupling layer comprising asecond dielectric layer comprising a material which is substantiallytransparent to said at least one laser beam wavelength, selected fromthe group consisting of: SiN_(x), where x=ca. 0.8-1.33; AlN_(x), wherex=ca. 1-1.5: SiO_(x), where x=ca. 1-2.0m; and AlO_(x), where x=ca. 1-1.5; (g) an MO read-out layer comprising an RE-TM material selected fromthe group consisting of: GdFeCo and GdFeCoX, where X is Al, Nd, or Y,and GdFeCoXX′, where X is Al, Nd, or Y and X′ is Cr, Ta, or Nb; and (h)a third dielectric layer comprising a material which is substantiallytransparent to said at least one laser beam wavelength and selected fromthe group consisting of: SiN_(x), where x=ca. 0.8-1.33; AlN_(x), wherex=ca. 1-1.5; SiO_(x), where x=ca. 1-2.0; and AlO_(x), where x=ca. 1-1.5;wherein said protective overcoat layer is formed on said thirdtransparent dielectric layer and said lubricant topcoat layer is formedon said protective overcoat layer.
 16. The medium according to claim 15,comprising another layer stack, identical to the abovesaid layer stack,formed on the other one of said pair of opposed major surfaces of saidsubstrate.